Method and apparatus for operating subframe and transmitting channel information for controlling interference in communication system

ABSTRACT

A method and an apparatus for operating a subframe and transmitting channel information for controlling interference in a communication system are provided. If a macro evolved Node B (eNodeB) determines and reports an uplink protection subframe for suppressing uplink transmission to a neighboring eNodeB, transmits scheduling information for uplink data through a downlink subframe corresponding to an uplink protection subframe, and the uplink protection subframe determined by the neighboring eNodeB is reported, a small eNodeB sets the reported uplink protection subframe as a flexible subframe, and uses the flexible subframe for downlink transmission. If the flexible subframe is used for the downlink transmission, a terminal of the small eNodeB measures and transmits non-period channel information in the flexible subframe through at least one uplink subframe.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Koreanpatent application filed on Apr. 12, 2011 in the Korean IntellectualProperty Office and assigned Serial No. 10-2011-0033916, the entiredisclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cellular wireless communicationsystem. More particularly, the present invention relates to a method ofcontrolling interference between different cells in a Time-DivisionDuplex (TDD) communication system for supporting a flexible subframe anda method of transmitting channel information by a terminal when anevolved Node B (eNodeB) schedules data through the flexible subframe.

2. Description of the Related Art

In recent years, an Orthogonal Frequency Division Multiple Access(OFDMA) scheme or a Single Carrier-Frequency Division Multiple Access(SC-FDMA) scheme similar thereto has been used as a scheme fortransmitting high speed data through a wireless channel. The foregoingmultiple access scheme allots and operates time-frequency resources thatcarry data or control information for each user in a non-overlappingmanner, namely, to achieve orthogonality of the data or controlinformation of each user.

An important consideration is support of a scalable bandwidth to providehigh speed wireless data service in a cellular wireless communicationsystem. As an example, a Long Term Evolution (LTE) system may havevarious bandwidths such as 20/15/10/5/3/1.4 MHz. Service providers mayselect one from among the foregoing bandwidths to provide service. Theremay be a plurality of types of terminals including a type supporting amaximum of up to 20 MHz of bandwidth and a minimum as small as 1.4 MHzof bandwidth. An LTE-Advanced (LTE-A) system, which is aimed atproviding service that meets an International Mobile Telecommunications(IMT)-Advanced requirement, may provide a wideband service up to amaximum of 100 MHz of bandwidth by using LTE Carrier Aggregation (CA).

The LTE-A system uses a wider band than the LTE system for transmittinghigh speed data. Also, because backward compatibility with respect toLTE terminals is important, LTE terminals may access the LTE-A system toreceive a service. To do this, the LTE-A system divides a total systemband into sub-bands or Component Carriers (CCs) of a bandwidth capableof transmitting or receiving by an LTE terminal, combines apredetermined CC, and generates and transmits data for each CC tosupport high speed data transmission of the LTE-A system for each CCusing a transmission/reception process of the LTE system. The CC mayalso be referred to as a cell. Each CC (or cell) is divided into aPrimary Cell (PCell) and a Secondary Cell (SCell) in an application orimportance in an aspect of a terminal. In an aspect of a terminal, theprimary cell is one cell, and the secondary cell is any remaining cellexcept for the primary cell. In the LTE-A system, an uplink controlchannel may be transmitted in only the primary cell and an uplink datachannel may be transmitted in the primary cell and the secondary cell.

Scheduling information with respect to data to be transmitted for eachCC is reported to a terminal as Downlink Control Information (DCI). TheDCI defines various formats to apply and operate a determined DCI formataccording to which it is scheduling information with respect to uplinkdata, scheduling information with respect to downlink data, a compactDCI, a DCI for power control, or spatial multiplexing using a multipleantenna. For example, a DCI format 1 being control information withrespect to downlink data not applying a Multiple Input Multiple Output(MIMO) antenna is composed of control information as one or more asfollows.

-   -   Resource allocation type 0/1 flag: notifies whether a resource        allotment type is type 0 or type 1. Type 0 applies a bitmap type        to allot a resource for each Resource Block Group (RBG). A        fundamental unit of scheduling in LTE and LTE-A systems is a        Resource Block (RB) expressed as time and frequency region        resources. The RBG is configured by a plurality of RBs and        becomes a fundamental unit of scheduling in type 0. Type 1        allots a certain RB in the RBG.    -   Resource block assignment: notifies of a RB allotted in data        transmission. A resource expressed according to system bandwidth        and resource allotment type is determined.    -   Modulation and coding scheme: notifies a modulation schemed and        coding rate used in data transmission.    -   Hybrid Automatic Repeat Request (HARQ) process number: notifies        a process number of HARQ.    -   New data indicator: notifies whether it is an HARQ initial        transmission or a retransmission.    -   Redundancy version: notifies a redundancy version of an HARQ.    -   Transmission Power Control (TPC) command for Physical Uplink        Control Channel (PUCCH): notifies a power control command with        respect to a PUCCH being an uplink control channel.

The DCI is transmitted through a Physical Downlink Control Channel(PDCCH) being a downlink physical control channel via a channel codingand modulation procedure.

However, there is a problem in that interference between cells in theforgoing wireless communication system occurs. That is, a signal betweenan evolved Node B (eNodeB) and a terminal in each cell acts as mutualinterference to a terminal of an adjacent cell. Due to this, theperformance of the wireless communication system is deteriorated.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a method and an apparatus for operating asubframe and transmitting channel information for controllinginterference in a communication system.

In accordance with an aspect of the present invention, a method oftransmitting channel information by a terminal for controllinginterference is provided. The method includes determining whether asubframe is a flexible subframe used for downlink transmission,measuring non-period channel information in the flexible subframe, whenthe subframe is the flexible subframe used for the downlinktransmission, and transmitting data including the non-period channelinformation in the measured flexible subframe through at least oneuplink subframe.

In accordance with another aspect of the present invention, a method ofreceiving channel information by an eNodeB for controlling interferenceis provided. The method includes determining whether a subframe is aflexible subframe used for downlink transmission, and receiving dataincluding non-period channel information in the flexible subframe in atleast one uplink subframe after the flexible subframe.

In accordance with another aspect of the present invention, a terminalfor transmitting channel information for controlling interference isprovided. The terminal includes a transceiver for transmitting andreceiving information to and from an eNodeB, respectively, and acontroller for determining whether a subframe is a flexible subframeused for downlink transmission based on information received from theeNodeB, for measuring non-period channel information in the flexiblesubframe, when the subframe is used for the downlink transmission, andfor controlling to transmit data including the non-period channelinformation from the flexible subframe to the at least one uplinksubframe.

In accordance with another aspect of the present invention, an eNodeBdevice for receiving channel information for controlling interference isprovided. The eNodeB device includes a transceiver for transmitting andreceiving information to and from an eNodeB, respectively, and acontroller for controlling the transceiver to transmit informationindicating whether a subframe is a flexible subframe used for downlinktransmission to the terminal, and to receive data including non-periodchannel information in the flexible subframe in at least one uplinksubframe after the flexible subframe.

In accordance with another aspect of the present invention, a method ofoperating a subframe of an eNodeB for controlling interference isprovided The method includes determining an uplink protection subframesuppressing an uplink transmission, transmitting the determined uplinkprotection subframe to a neighboring eNodeB, and transmitting schedulinginformation for uplink data in a downlink subframe corresponding to theuplink protection subframe.

In accordance with another aspect of the present invention, a method ofoperating a subframe of an eNodeB for controlling interference isprovided. The method includes receiving an uplink protection subframesuppressing uplink transmission by a neighboring eNodeB, determining aflexible subframe based on the uplink protection subframe, and using theflexible subframe for downlink transmission.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating an example of an operation of asub-frame in a Time-Division Duplex (TDD) frame according to anexemplary embodiment of the present invention;

FIG. 2 is a diagram illustrating another example of an operation of asubframe in a TDD frame according to an exemplary embodiment of thepresent invention;

FIG. 3 is a diagram illustrating an example of a configuration of asub-frame in a TDD frame according to an exemplary embodiment of thepresent invention;

FIG. 4 is a conceptual diagram illustrating a communication system foroperating a TDD frame according to an exemplary embodiment of thepresent invention;

FIG. 5 is a diagram illustrating an example for describing arelationship between sub-frames in a TDD frame according to an exemplaryembodiment of the present invention;

FIGS. 6A and 6B are flowcharts illustrating a method of operating anevolved Node B (eNodeB) in a communication system according to anexemplary embodiment of the present invention;

FIGS. 7A, 7B, 7C, and 7D are flowcharts illustrating channel informationtransmitting methods by a terminal in a communication system accordingto first, second, third, and fourth exemplary embodiments of the presentinvention, respectively;

FIGS. 8A and 8B are diagrams illustrating examples of a channelinformation transmitting procedure of a terminal according to the firstexemplary embodiment of the present invention;

FIG. 9 is a block diagram illustrating an apparatus for operating asub-frame of an eNodeB in a communication system according to anexemplary embodiment of the present invention; and

FIG. 10 is a block diagram illustrating an apparatus for transmittingchannel information of a terminal in a communication system according toan exemplary embodiment of the present invention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

While exemplary embodiments of the present invention may be described inthe context of a Time-Division Duplex (TDD) system for convenience indescription, the present invention is equally applicable to othercommunication systems having a similar technical background and channelforms by applying variations and modifications falling within the spiritand scope of the present invention, as would be apparent to thoseskilled in the art.

A TDD communication system uses a common frequency in downlink anduplink, and distinctively operates transmission/reception of an uplinksignal and a downlink signal in the time domain. The Long Term Evolution(LTE) TDD system distinctively transmits an uplink or downlink signalfor each sub-frame. According to a traffic load of uplink and downlink,a subframe for uplink/downlink is equally divided and operated in thetime domain, more subframes are allotted and operated in the downlink,or more subframes are allotted and operated in the uplink. In the LTEsystem, the length of the subframe is 1 ms, and ten subframes constructone radio frame.

TABLE 1 Uplink- downlink Subframe number configuration 0 1 2 3 4 5 6 7 89 0 D S U U U D S U U U 1 D S U U D D S U U D 2 D S U U D D S U D D 3 DS U U U D D D D D 4 D S U U D D D D D D 5 D S U D D D D D D D 6 D S U UU D S U U D

Table 1 illustrates a TDD Uplink-Downlink (TDD UL-DL) configuration. InTable 1, ‘D’ indicates a subframe set for downlink transmission, ‘U’indicates a subframe set for uplink transmission, and ‘S’ indicates aSpecial subframe composed of a Downlink Pilot Time Slot (DwPTS), a GuardPeriod (GP), and a Uplink Pilot Time Slot (UpPTS). In DwPTS, controlinformation may be transmitted through the downlink in the same manneras in a general subframe, and downlink data transmission is possibleaccording to a set state of a special subframe when the length of theDwPTS is sufficiently long. The GP is a section for the switching of atransmission state from the downlink to uplink, and the length of the GPis determined according to a network setting or the like. The UpPTS isused to transmit a Sounding Reference Signal (SRS) used for estimatingan uplink channel state or a Random Access Channel (RACH) for a terminalfor random access.

For example, in a case of TDD UL-DL configuration #6, downlink data andcontrol information may be transmitted to subframes #0, #5, #9, anddownlink data and control information may be transmitted to subframes#2, #3, #4, #7, #8. Further, downlink control information and downlinkdata according to conditions may be transmitted in subframes #1 and #6corresponding to a special subframe and SRS or RACH may be transmittedthrough uplink.

Because the transmission of a downlink or uplink signal is allowableduring a certain time period in the TDD system, there is a need fordefining a special timing relationship between uplink/downlink physicalchannels having correlation such as a control channel for datascheduling, a scheduled data channel, and a Hybrid Automatic RepeatRequest (HARQ) ACKnowledgment (ACK)/Negative-ACKnowledgment (NACK)channel corresponding to a data channel.

The following is an uplink/downlink timing relation between a PhysicalDownlink Shared Channel (PDSCH) being a physical channel fortransmitting downlink data and a Physical Uplink Control Channel (PUCCH)or a Physical Uplink Shared Channel (PUSCH) being a physical channel towhich a corresponding uplink HARQ ACK/NACK is transmitted.

When receiving a PDSCH carried to a subframe n-k from the eNodeB, theterminal transmits uplink HARQ ACK/NACK with respect to the PDSCH to anuplink subframe n. In this case, k is a structural element of set K, andK is defined in Table 2.

TABLE 2 UL-DL Subframe n configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 —— 6 — 4 1 — — 7, 6 4 — — — 7, 8 4 — 2 — — 8, 7, 4, — — — — 8, 7, — — 64, 6 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 6, 5, — — — — —— 11 4, 7 5 — — 13, 12, — — — — — — — 9, 8, 7, 5, 4, 11, 6 6 — — 7 7 5 —— 7 7 —

Table 3 rearranges to which subframe a corresponding uplink HARQACK/NACK is carried according to the definition of Table 2 when a PDSCHin a TDD UL-DL configuration is carried to each downlink subframe (D) ora special subframe (S)n.

TABLE 3 UL-DL Subframe n configuration 0 1 2 3 4 5 6 7 8 9 0 D4 S6 U U UD4 S6 U U U 1 D7 S6 U U D4 D7 S6 U U D4 2 D7 S6 U D4 D8 D7 S6 U D4 D8 3D4 S11 U U U D7 D6 D6 D5 D5 4 D12 S11 U U D8 D7 D7 D7 FS D4 5 D12 111 UD9 D8 D7 D6 D6 D4 D13 6 D7 S7 U U U D7 S7 U U D5

FIG. 1 is a diagram illustrating an example of an operation of asub-frame in a TDD frame according to an exemplary embodiment of thepresent invention. Table 3 will be described using FIG. 1. In this case,FIG. 1 is a diagram illustrating to which subframe a correspondinguplink HARQ ACK/NACK is carried according to the definition of Table 3when a PDSCH in a TDD UL-DL configuration #6 of Table 3 is carried toeach downlink or special subframe.

Referring to FIG. 1, a terminal transmits an uplink HARQ ACK/NACKcorresponding to a PDSCH 101 which an evolved Node B (eNodeB) transmitsto a subframe #0 of a radio frame i to a subframe #7 of a radio frame i(103). In this case, Downlink Control Information (DCI) includingscheduling information with respect to the PDSCH 101 is transmitted tothe same subframe as a subframe to which the PDSCH is transmittedthrough the PDCCH. As another example, the terminal transmits an uplinkHARQ ACK/NACK corresponding to the PDSCH 105 which the eNodeB havingcarried to a subframe #9 of a radio frame i to a subframe #4 of a radioframe i+1 (107). In the same manner, downlink control information DCIincluding scheduling information with respect to the PDSCH 105 istransmitted to the same subframe as the subframe to which the PDSCH istransmitted through the PDCCH.

In the LTE system, downlink HARQ uses an asynchronous HARQ scheme inwhich a data retransmission time point is not fixed. That is, whenreceiving feedback of HARQ NACK with respect to HARQ initialtransmission data transmitted by the eNodeB from a terminal, the eNodeBfreely determines a transmission time point of retransmission data of anext HARQ by a scheduling operation. As a decoding result with respectto received data for an HARQ operation, after buffering HARQ datadetermined as including an error, it is combined with next HARQretransmission data. In this case, so as to maintain a received buffercapacity of the terminal within a predetermined limit, the maximumnumber of downlink HARQ processed for each TDD UL-DL configuration isdefined as illustrated in a following Table 4. One HARQ process ismapped to one subframe in the time domain.

TABLE 4 TDD UL/DL configuration Maximum number of HARQ processes 0 4 1 72 10 3 9 4 12 5 15 6 6

Referring to FIG. 1, the terminal decodes a PDSCH (101) in a subframe #0of a radio frame i to which an eNodeB transmits. If it is determinedthat the decoded PDSCH includes an error, the terminal transmits a HARQNACK to a subframe #7 of a radio frame I (103). When receiving the HARQNACK, the eNodeB configures retransmission data with respect to thePDSCH (101) by a PDSCH (109) and transmits it together with the PDCCH.The example of FIG. 1 illustrates that the retransmission data arecarried to a subframe #1 of a radio frame i+1 by reflecting that amaximum number of downlink HARQ processes of TDD UL-DL configuration #6according to definition of Table 4. That is, there are a total of 6downlink HARQ processes (111, 112, 113, 114, 115, and 116) between aninitial transmission PDSCH 101 and a retransmission PDSCH 109.

In the LTE system, the uplink HARQ uses a synchronous HARQ scheme inwhich a data transmission time point is fixed unlike a downlink HARQ.That is, an uplink/downlink timing relation of a Physical Uplink SharedChannel (PUSCH) being a physical channel for transmitting uplink data, aPDCCH being a preceding downlink control channel thereof, and a PhysicalHybrid Indicator Channel (PHICH) being a physical channel to which adownlink HARQ ACK/NACK corresponding to the PUSCH is transmitted isfixed by a rule described below.

When receiving a PDCCH including uplink scheduling control informationprovided from an eNodeB or a PHICH to which a downlink HARQ ACK/NACK istransmitted, the terminal transmits uplink data corresponding to thecontrol information to a subframe n+k through a PUSCH. In this case, kis defined in Table 5 as follows.

TABLE 5 TDD UL/DL DL subframe number n configuration 0 1 2 3 4 5 6 7 8 90 4 6 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 4 4 5 4 6 7 7 7 7 5

Further, when the terminal receives a PHICH carrying a downlink HARQACK/NACK from an eNodeB in a subframe, the PHICH corresponds to a PUSCHwhich the terminal transmits to a subframe i−k. In this case, k is asdefined in Table 6 as follows.

TABLE 6 TDD UL/DL DL subframe number n configuration 0 1 2 3 4 5 6 7 8 90 7 4 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6 4 7 4 6

FIG. 2 is a diagram illustrating another example of an operation of asub-frame in a TDD frame according to an exemplary embodiment of thepresent invention. In this case, FIG. 2 is a diagram illustrating towhich subframe an uplink PUSCH corresponding to a PDCCH or a PHICH whenthe PDCCH or the PHICH is carried to each downlink or special subframe,and to which subframe a PHICH corresponding to the PUSCH is carriedaccording to definitions of Table 5 and Table 6 in a case of TDD UL-DLconfiguration #1.

Referring to FIG. 2, the terminal transmits a PDCCH provided from aneNodeB through a subframe #1 of a radio frame i or an uplink PUSCHcorresponding to a PHICH (201) through a subframe #7 of a radio frame i(203). Further, the eNodeB transmits a PHICH corresponding to the PUSCHto the terminal through a subframe #1 of a radio frame i+1 (205). Asanother example, the terminal transmits a PDCCH provided from the eNodeBthrough a subframe #6 of a radio frame i or an uplink PUSCHcorresponding to the PHICH (207) through a subframe #2 of a radio framei+1 (209). Moreover, the eNodeB transmits a PHICH corresponding to thePUSCH to the terminal through a subframe #6 of a radio frame i+1 (211).

The LTE TDD system restricts downlink transmission of a PDCCH or a PHICHcorresponding to the PUSCH associated with transmission of a PUSCH in acertain downlink subframe to secure minimum transmission/receptionprocessing times of an eNodeB and a terminal. For example, in a case ofTDD UL-DL configuration #1, a PDCCH for scheduling the PUSCH or a PHICHcorresponding to the PUSCH are not transmitted in the downlink throughsubframes #0 and #5.

In general, because the number of subframes for transmitting uplink andthe number of subframes for transmitting downlink are determined afterTDD UL-DL configuration is determined, it may not be possible toactively process a case where a certain eNodeB requires data having moredownlink transmission than uplink transmission in a certain eNodeB at acertain time point. A flexible subframe approach capable of dynamicallychanging a TDD UL-DL configuration of an entire system instead ofchanging the TDD UL-DL according to a data request capacity of theuplink/downlink in a certain eNodeB has been suggested. The flexiblesubframe may be allotted from an uplink subframe existing in front ofdownlink subframe to an uplink subframe continuously adjacent on thetime axis so as not to influence a protection time which should bebetween a downlink subframe and the uplink subframe.

FIG. 3 is a diagram illustrating an example of a configuration of asub-frame in a TDD frame according to an exemplary embodiment of thepresent invention. In this case, FIG. 3 is a diagram illustrating anexample of applying a flexible subframe to TDD UL-DL configuration #3.

Referring to FIG. 3, when the flexible subframe is not operated, a framemay be configured as 301. Further, when one flexible subframe isoperated, the frame may be configured as 302. In this case, one uplinksubframe neighboring a downlink subframe among the uplink subframes isoperated as a flexible subframe as illustrated in 309. In other words, asubframe #4 may be operated as a flexible subframe. Further, when aplurality of flexible subframes is operated, the frame may be configuredas 303 and 304. In this case, at least two adjacent uplink subframesneighboring a downlink subframe are operated as flexible subframes asillustrated in 310 and 311 in 303 and (312, 313, and 314 in 304). Here,the flexible subframes continuously appear between downlink subframes.That is, when the subframe #3 is used for downlink transmission as aflexible subframe, the subframe #4 should always be used for downlinktransmission together with the subframe #3 as the flexible frame afterthe subframe #3. In the same manner, when the subframe #2 is used fordownlink transmission as the flexible subframe, the uplink subframe #3and the uplink subframe #4 should be used for downlink transmissiontogether with the subframe #2 as a flexible frame. In this case,according to the implementation, the eNodeB may notify the uplinksubframe operating as a flexible subframe to the terminal using separateinformation or signaling. Further, the terminal may discriminate anuplink subframe operated as the flexible subframe itself withoutseparate information or signaling. Further, when there are p flexiblesubframes corresponding to an integer including a special subframe and adownlink subframe firstly appearing after the special subframe, forexample, a subframe #n between a subframe #n+1, the flexible subframesare subframes from a subframe #n−p+1 to a subframe #n, which aresubframes neighboring each other on a time axis. Further, when the frameincludes at least two uplink subframes to be spaced apart from eachother on the time axis, a part of the uplink subframes may be operatedas a flexible subframe.

FIG. 4 is a conceptual diagram illustrating a communication system foroperating a TDD frame according to an exemplary embodiment of thepresent invention. In this case, FIG. 4 is a diagram illustrating acertain eNodeB using a flexible subframe for downlink transmission whenthere is a plurality of eNodeBs and the eNodeBs are operated with thesame TDD UL-DL configuration.

Referring to FIG. 4, when a macro eNodeB originally uses a correspondingflexible subframe for uplink transmission, and a small eNodeB locatednearby uses a corresponding flexible subframe for downlink transmission,a small eNodeB terminal having received downlink transmission from asmall eNodeB is interfered by a nearby macro eNodeB terminaltransmitting an uplink to a macro eNodeB. The interference is shown inFIG. 4 as a dotted arrow. Accordingly, when the small eNodeB uses theflexible subframe for downlink transmission, there is a need for anapproach for receiving the downlink without the small eNodeB terminalreceiving interference. The corresponding approach should not influenceuse of a resource of the macro eNodeB.

Further, when the small eNodeB uses a flexible subframe for downlinktransmission, the small eNodeB needs channel information capable ofbeing referred when scheduling downlink data. However, there is a needfor notifying channel information to a small eNodeB by a small eNodeBterminal in a state where an interference situation entirely differsfrom a previous situation prior to a flexible subframe, in a state wherethere is interference due to downlink transmission of an adjacent macroeNodeB, interference due to operating a flexible subframe to transmituplink or downlink by a neighboring small eNodeB.

Here, in the present exemplary embodiment, when a small eNodeB uses aflexible subframe for downlink transmission in a TDD system, a smalleNodeB terminal controls interference caused from the macro eNodeBterminal so as not to influence resource use of the macro eNodeB.

A method is now described in which the small eNodeB transmits downlinkchannel information capable of being referred upon scheduling downlinkdata by a small eNodeB when the small eNodeB uses the flexible subframefor downlink transmission in the TDD system.

First, the method is described in which a small eNodeB terminal controlsinterference received from a macro eNodeB terminal, which does notinfluence use of a resource of the macro eNodeB when a small eNodeB usesa flexible subframe for downlink transmission in the TDD wirelesscommunication system.

FIG. 5 is a diagram illustrating an example for describing arelationship between sub-frames in a TDD frame according to an exemplaryembodiment of the present invention. In this case, FIG. 5 is a diagramcomparing PUSCH transmission timing with PUCCH transmission timingaccording to a PDCCH through TDD UL-DL configuration #3. The PUSCHtransmission timing according to the PDCCH is shown in Table 5 and thePUCCH timing according to a PDCCH is shown in Table 3.

Referring to FIG. 5, reference numeral 501 illustrates a timingrelationship with respect to TDD UL-DL configuration #3 in Table 3 andTable 5. Reference numeral 502 illustrates a timing relationship withrespect to TDD UL-DL configuration #4 in Table 3 and Table 5.

It can be appreciated that a PUSCH is generated in a subframe #4according to control information for a PUSCH of a PDCCH in a subframe #0and a PUCCH is generated in a subframe #4 according to controlinformation for a PUCCH of a PDCCH in a subframe #0. Further, it can beappreciated that a PUCCH is generated in a subframe #4 according tocontrol information for a PUCCH of a PDCCH in a subframe #9.Accordingly, when the subframe #4 is set as a flexible subframe, themacro eNodeB of FIG. 4 may set subframes #0 and #9 as a Blankingsubframe without PDCCH transmission such that uplink interference is notinterfered in the subframe #4. The small eNodeB of FIG. 4 sets asubframe #4 as a flexible subframe based on information with respect tothe Blanking subframe, and uses the flexible subframe, and a terminal ofa small eNodeB may receive downlink transmission without interference.However, when a macro eNodeB does not transmit a PDCCH through asubframe #9, because a PUSCH is generated from the subframe #3 accordingto control information for a PUSCH of a PDCCH in the subframe #9, it canbe appreciated that the PUSCH in the subframe #3 not influencing anoperation of a flexible subframe of the small eNodeB is prevented tocause resource consumption of the macro eNodeB.

Accordingly, the present exemplary embodiment suggests that uplinkprotection subframe information being information limiting PUCCHtransmission of a macro eNodeB is transmitted to neighboring eNodeBsinstead of notifying blanking information with subframes #0 and #9 asillustrated in reference numeral 501. In the present exemplaryembodiment, the macro eNodeB may not transmit control information for aPUCCH through a PDCCH in a subframe #0 to restrict PUCCH transmissionthrough a subframe #4. Moreover, in the present exemplary embodiment, amacro eNodeB may transmit control information for a PUSCH through aPDCCSH in a downlink subframe #9 to restrict a PUCCH through thesubframe #4. That is, the macro eNodeB may transmit a PUSCH in asubframe #3 through control information for a PUSCH of a PDCCH in asubframe #9. A neighboring small eNodeB having received the uplinkprotection subframe information may set the subframe #4 as a flexiblesubframe and perform downlink transmission through the flexiblesubframe, and a terminal of a small eNodeB may receive the downlinktransmission without interference.

In substantially the same manner, as illustrated in reference numeral502, it can be appreciated that a PUSCH is generated from a subframe #3according to control information for a PUSCH of a PDCCH in the subframe#9, and a PUCCH is generated from the subframe #3 according to controlinformation for a PUCCH of a PDCCH in the subframe #9. Further, it canbe appreciated that a PUCCH is generated from a subframe #3 according tocontrol information for a PUCCH of a PDCCH in a subframe #8.Accordingly, when the subframe #3 is set as a flexible subframe, themacro eNodeB of FIG. 4 may set subframes #9 and #8 as a blankingsubframe not carrying the PDCCH not to prevent the occurrence of uplinkinterference in the subframe #3, and transmit the information to aneighboring eNodeB. A small eNodeB sets the subframe #3 as the flexiblesubframe based on the information with respect to the blanking subframe,and performs downlink transmission in the flexible subframe such that aterminal of the small eNodeB may receive the downlink transmissionwithout interference. However, when a PDCCH is not transmitted through asubframe #8 of a macro eNodeB, because a PUSCH is generated from thesubframe #2 according to control information for a PUSCH of a PDCCHthrough the subframe #8, it can be appreciated that resource consumptionoccurs by preventing PUSCH transmission through a subframe #2 notinfluencing an operation of a flexible subframe of the small eNodeB.Accordingly, as illustrated previously, the present exemplary embodimentsuggests an approach of transmitting uplink protection subframeinformation being information restricting PUCCH transmission of a macroeNodeB in the subframe #3 instead of notifying blanking information withrespect to subframes #8 and #9. Through this approach, the macro eNodeBmay not transmit control information for a PUCCH through a PDCCH in thesubframe #9 to restrict PUCCH transmission through the subframe #3.Furthermore, in the present exemplary embodiment, the macro eNodeB maytransmit control information for a PUSCH through a PDCCH in a downlinksubframe #8 to restrict PUCCH transmission through the subframe #3. Thatis, the macro eNodeB may perform PUSCH transmission in the subframe #2through control information for a PUSCH of a PDCCH through the subframe#8. A neighboring small eNodeB having received the uplink protectionsubframe information may set the subframe #3 as a flexible subframe andperform downlink transmission through the flexible frame, and a terminalof a small eNodeB may receive the downlink transmission withoutinterference.

FIG. 6A is a flowchart illustrating a method of operating an eNodeB in acommunication system according to an exemplary embodiment of the presentinvention.

Referring to FIG. 6A, a macro eNodeB transmits uplink protectionsubframe information to neighboring eNodeBs in step 601. In this case,the macro eNodeB determines and notifies an uplink protection subframefor suppressing uplink transmission in a terminal of a macro eNodeB toneighboring eNodeBs. Here, the neighboring eNodeB may be another macroeNodeB and a small eNodeB. To do this, the macro eNodeB may transmitpresence of determination of an uplink protection subframe with respectto each subframe through a bitmap corresponding to entire subframes.Meanwhile, the macro eNodeB may transmit presence of determination of anuplink protection subframe with respect to each uplink subframe througha bitmap corresponding to uplink subframes in a corresponding TDD UL-DLconfiguration. In the meantime, the macro eNodeB may transmit anindicator indicating a frame configuration including an uplinkprotection subframe implemented in a corresponding TDD UL-DLconfiguration, for example, one frame configuration of referencenumerals 301, 302, 303, or 304. Here, when a subframe is operatedaccording to a TDD UL-DL configuration #3, the macro eNodeB maydetermine at least one of subframe #2, #3, or #4 as an uplink protectionsubframe. The macro eNodeB performs scheduling in step 602. In thiscase, the macro eNodeB may not perform scheduling with respect to theuplink protection subframe such that uplink transmission is not achievedfrom a terminal of the macro eNodeB through the uplink protectionsubframe. The macro eNodeB transmits scheduling information according toa scheduling result in step 603. In this case, the macro eNodeBtransmits scheduling information of a PUSCH in a downlink subframecorresponding to an uplink protection subframe. Here, when a subframe isoperated according to a TDD UL-DL configuration #3, the macro eNodeBdoes not transmit scheduling information of a PUCCH in a subframe #9 buttransmits scheduling information of a PUSCH.

Meanwhile, although not shown, if an uplink protection subframedetermined by a neighboring eNodeB is notified, the macro eNodeB may seta corresponding uplink protection subframe. Further, the eNodeB performsscheduling. In this case, the macro eNodeB does not perform schedulingwith respect to the uplink protection subframe such that uplinktransmission is not achieved through the uplink protection subframe.Next, the macro eNodeB transmits scheduling information according to ascheduling result. In this case, the macro eNodeB transmits schedulinginformation for a PUSCH through a downlink subframe corresponding to anuplink protection subframe. Here, when the subframe is operatedaccording to a TDD UL-DL configuration #3, the macro eNodeB does nottransmit scheduling information for a PUCCH in a subframe #9 buttransmits scheduling information for a PUSCH.

FIG. 6B is a flowchart illustrating a method of operating a subframe ofa small eNodeB in a communication system according to an exemplaryembodiment of the present invention.

Referring to FIG. 6B, a small eNodeB receives uplink protection subframeinformation from neighboring eNodeBs in step 604. The small eNodeB setsa flexible subframe using the uplink protection subframe information instep 605. The small eNodeB uses the flexible subframe for downlinktransmission in step 606.

Through this, a terminal of a macro eNodeB does not perform uplinktransmission through an uplink protection subframe. Further, theterminal of the small eNodeB performs downlink transmission using anuplink protection subframe of a macro eNodeB as a flexible subframe.Accordingly, interference of the terminal of the small eNodeB issuppressed from a terminal of the macro eNodeB. That is, the terminal ofthe small eNodeB may receive downlink transmission without interference.

Next, a method is described in which the small eNodeB terminal transmitsdownlink channel information capable of being referred upon schedulingdownlink data by a small eNodeB when the small eNodeB uses the flexiblesubframe for downlink transmission in the TDD system. Prior todescribing the method, it may be assumed that there is no uplinktransmission in a neighboring macro eNodeB or a small eNodeB using amethod suggested in FIG. 5, FIG. 6A, and FIG. 6B when the small eNodeBuses a flexible subframe for downlink transmission. Accordingly, whenthere is neighboring small eNodeBs using the flexible subframe fordownlink transmission, an approach capable of knowing channelinformation including downlink interference from corresponding smalleNodeBs is provided.

FIG. 7A is a flowchart illustrating channel information transmittingmethods by a terminal of a small eNodeB in a communication systemaccording to the first exemplary embodiment of the present invention.

Referring to FIG. 7A, a terminal determines whether a small eNodeB usesa flexible subframe for downlink transmission in step 701. Thecorresponding determination decodes a PDCCH in a region which the PDCCHof the flexible subframe may exist to determine whether there is a DLDCI format transmitted to the terminal. If there is no DL DCI format,the terminal determines whether transmission of uplink data is performedaccording to presence of scheduling with respect to uplink data in aprevious downlink subframe and performs the transmission of uplink datain step 709. If there is the DL DCI format, the terminal may know thatthe flexible subframe is used for downlink transmission and measuresnon-period channel information in a corresponding subframe in step 702.The terminal transmits the non-period channel information through anuplink subframe appearing after an n+4 subframe in step 703. That is,the terminal may measure the non-period channel information through theflexible frame without a separate request from a small eNodeB.

If the subframe #4 is set as a flexible subframe in reference numeral501 and a small eNodeB uses the flexible subframe for downlinktransmission, the terminal transmits the non-period channel informationthrough a subframe #2 of a next radio frame. Concrete contents of thenon-period channel information may be previously set according to atransmission mode set in the terminal, and may be transmitted throughupper layer signaling. For example, the contents of the non-periodchannel information may be a periodic band, namely, channel qualityindicator (CQI)/Precoding Matrix Indicator (PMI), or a periodic sub-bandCQI/PMI. In a case of the periodic sub-band CQI/PMI, the number and thesize of sub-bands may be previously determined and may be transmittedthrough upper layer signaling. Further, a Rank Indicator (RI) may betransmitted. As described above, the terminal may selectively transmitnon-period channel information and periodic channel information to theeNodeB according to whether a flexible subframe is used for downlinktransmission. To selectively transmit the channel information, theterminal may store the periodic channel information and the non-periodchannel information. A transmission order and the transmission number ofchannel information such as the wideband CQI/PMI, the sub-band CQI/PMI,and RI may be previously determined according to an importance of thechannel information or the number of uplink subframes according to a TDDUL-DL configuration, and may be transmitted through upper layersignaling. If there is another upper layer control signal to betransmitted at step 703 or upper layer data, they may be simultaneouslymultiplexed and transmitted. A part of the upper layer controlinformation or upper layer data may not be transmitted through apredetermined method or upper layer signaling.

Subsequently, the terminal determines whether a small eNodeB uses aflexible subframe for downlink transmission through an operation of step704 in a flexible subframe appearing afterward. When the flexiblesubframe is used for downlink transmission, the terminal stopstransmission of non-period channel information with respect to aprevious flexible subframe, and measures the non-period channelinformation in a corresponding subframe in step 705. Next, the processreturns to step 703 and performs a corresponding operation.

If the flexible subframe is not used for downlink transmission at step704, the terminal determines whether the predetermined transmissionnumber of non-period channel information is satisfied in step 706. Ifthe predetermined transmission number of non-period channel informationis satisfied, the terminal determines whether transmission of uplinkdata is performed according to the presence of scheduling of a smalleNodeB and performs the transmission of uplink data in step 707. If thepredetermined transmission number of non-period channel information isnot satisfied at step 706, the terminal transmits non-period channelinformation with respect to a flexible subframe in uplink subframe instep 708. In this case, transmitted non-period channel information to betransmitted is determined according a predetermined transmission orderof channel information. If there is another upper layer controlinformation or upper layer data to be transmitted at step 708, they maybe multiplexed and transmitted. The process then returns to step 704 andperforms a corresponding operation.

FIGS. 8A and 8B are diagrams illustrating examples of a channelinformation transmitting procedure of a terminal according to the firstexemplary embodiment of the present invention.

Referring to FIG. 8A, reference numeral 801 illustrates detailednon-period channel information and a time point when a subframe #4 inTDD UL-DL configuration #3 is set as a flexible subframe, and downlinktransmission is performed. The small eNodeB performs downlinktransmission through a subframe #4 of an i-th radio frame, and theterminal detects a DCI format as illustrated at step 701 of FIG. 7A,recognizes that the subframe is performed for downlink transmission, andmeasures non-period channel information in the subframe. Next, theterminal transmits the non-period channel information measured in asubframe #2 of an (i+1)-th radio frame first appearing after an (n+4)-thframe. It is assumed in this exemplary embodiment that RI, wideband CQI,and sub-band CQI are set to be transmitted according to upper layersignaling. It is assumed that the transmission numbers of RI, widebandCQI, or sub-band CQI are set to 1, 1, and 4, respectively. It is assumedthat the transmission order is previously set in an order of RI,wideband CQI, a sub-band CQI, a sub-band CQI, a sub-band CQI, and asub-band CQI. The size of the sub-band may be previously set accordingto a downlink bandwidth size, and the downlink bandwidth may be set tobe divided into a set of plural sub-bands. Further, selection of thesub-bands may be set such that a terminal may select and inform one fromthe set of sub-bands to the eNodeB. An RI is firstly transmitted in asub-frame #2 of an (i+1)-th radio frame. A wideband CQI is transmittedin a subframe #3 of an (i+1)-th radio frame. Next, a sub-band CQI istransmitted in a subframe #4 of the (i+1)-th radio frame. Next, thesub-band CQI is transmitted from a subframe #3 to a subframe #4 of an(i+2)-th radio frame, respectively. The subframe #4 of an (i+3)-th radioframe is used for downlink transmission of the subframe by the smalleNodeB, and the terminal measures non-period channel information andtransmits channel information as set above.

Referring to FIG. 8B, reference numeral 802 illustrates detailednon-period channel information and a time point when subframes #3 and #4are set as a flexible subframe from a TDD UL-DL configuration #6, anddownlink transmission is performed. The small eNodeB performs downlinktransmission through subframes #3 and #4 of an i-th radio frame, and theterminal measures non-period channel information in the subframes #3 and#4. Subsequently, transmission of non-period channel informationmeasured from a subframe #8 of an i-th radio frame first appearing afteran (n+4) frame. It is assumed in this exemplary embodiment that widebandCQI and sub-band CQI are set to be transmitted according to upper layersignaling. It is assumed that the transmission numbers of a wideband CQIfor a subframe #3, a sub-band CQI, a wideband CQI for a subframe #4, anda sub-band CQI are set to 1, 2, 1, and 2, respectively. It is assumedthat the transmission order is previously set in an order of thewideband CQI for the subframe #3, a sub-band CQI, the sub-band CQI, awideband CQI for the subframe 4#, the sub-band CQI, and the sub-bandCQI. The size of the sub-band may be previously set according to adownlink bandwidth size, and the downlink bandwidth may be set to bedivided into a set of plural sub-bands. Further, selection of thesub-bands may be set such that a terminal may select and inform one fromthe set of sub-bands to the eNodeB. A wideband CQI for the subframe #3is firstly transmitted in a sub-frame #8 of an i-th radio frame. Awideband CQI for the subframe #3 is transmitted in a sub-frame #2 of an(i+1)-th radio frame. Next, a wideband CQI for the subframe #3 istransmitted in a sub-frame #3 of an (i+1)-th radio frame. Next, awideband CQI for the subframe #4 is transmitted in a sub-frame #4 of an(i+1)-th radio frame. Next, a wideband CQI for the subframe #4 istransmitted in a sub-frame #7 and a sub-frame #8 of an (i+1)-th radioframe, respectively. The subframe #4 of an (i+2)-th radio frame is usedfor downlink transmission of the subframe by the small eNodeB, and theterminal measures non-period channel information and transmits channelinformation with respect to the subframe #4 as set above.

FIG. 7B is a flowchart illustrating a method of transmitting channelinformation by a terminal of a small eNodeB in a communication systemaccording to a second exemplary embodiment of the present invention.Unlike the first exemplary embodiment of FIG. 7A and FIGS. 8A and 8B, asecond exemplary embodiment of FIG. 7B may transmit channel informationthrough a PUSCH.

Referring to FIG. 7B, the terminal determines whether a small eNodeBuses a flexible subframe for downlink transmission in step 711. Thecorresponding determination includes decoding a PDCCH in a region whichthe PDCCH of the flexible subframe may exist to determine whether thereis a DL DCI format transmitted to the terminal. If there is no DL DCIformat, the terminal determines whether transmission of uplink data isperformed according to presence of scheduling with respect to uplinkdata in a previous downlink subframe and performs the transmission ofuplink data in step 715. If there is the DL DCI format, it can beappreciated that the terminal may know that the flexible subframe isused for downlink transmission. The terminal receives a non-periodchannel information request from the flexible subframe provided from theeNodeB in step 712. The reception of a corresponding information requestmay be performed by a UL grant through PDCCH decoding as in step 711.The UL grant may be restricted by requesting only non-period channelinformation without PUSCH data. The terminal measures non-period channelinformation from a corresponding flexible subframe in step 713. Theterminal transmits non-period channel information according to a requestof non-period channel information through a UL grant at step 712 throughan uplink subframe appearing after an (n+4) subframe in step 714. Forexample, if the subframe #4 is set as a flexible subframe in referencenumeral 501 and a small eNodeB uses the flexible subframe for downlinktransmission, and the non-period channel information is requestedthrough the flexible subframe, the terminal transmits the non-periodchannel information through a subframe #2 of a next radio frame. Thenon-period channel information includes all of channel information sentby upper layer signaling.

FIG. 7C is a flowchart illustrating a method of transmitting channelinformation by a terminal of a small eNodeB in a communication systemaccording to a third exemplary embodiment of the present invention.Unlike the first exemplary embodiment of FIG. 7A and FIGS. 8A and 8B, athird exemplary embodiment of FIG. 7C may transmit channel informationthrough a PUSCH.

Referring to FIG. 7C, the terminal determines whether a small eNodeBuses a flexible subframe for downlink transmission in step 721. Thecorresponding determination decodes a PDCCH in a region which the PDCCHof the flexible subframe may exist to determine whether there is a DLDCI format transmitted to the terminal. If there is no DL DCI format,the terminal determines whether transmission of uplink data is performedaccording to presence of scheduling with respect to uplink data in aprevious downlink subframe and performs the transmission of uplink datain step 725. If there is the DL DCI format, the terminal may know thatthe flexible subframe is used for downlink transmission. The terminalmeasures non-period channel information through a corresponding flexiblesubframe in step 722. The information is measured to be transmitted whennon-period channel information for a corresponding flexible subframe isrequested. Step 722 may be performed after a next step according to animplementation operation of the terminal. The terminal receivesnon-period channel information request through a first downlink subframefrom an eNodeB after the flexible subframe in step 723. The non-periodchannel information request is received through the UL grant, and the ULgrant may be restricted to requesting only non-period channelinformation without PUSCH data. The terminal transmits non-periodchannel information for the flexible subframe through an uplink subframecorresponding to the downlink subframe in step 724. The non-periodchannel information contains all of channel information sent by upperlayer signaling.

FIG. 7D is a flowchart illustrating a method of transmitting channelinformation by a terminal of a small eNodeB in a communication systemaccording to a fourth exemplary embodiment of the present invention.Unlike the first exemplary embodiment of FIG. 7A and FIGS. 8A and 8B, afourth exemplary embodiment of FIG. 7D may transmit channel informationthrough a PUSCH.

Referring to FIG. 7D, the terminal determines whether a small eNodeBuses a flexible subframe for downlink transmission in step 731. Thecorresponding determination decodes a PDCCH in a region which the PDCCHof the flexible subframe may exist to determine whether there is a DLDCI format transmitted to the terminal. If there is no DL DCI format,the terminal determines whether transmission of uplink data is performedaccording to presence of scheduling with respect to uplink data in aprevious downlink subframe and performs the transmission of uplink datain step 737. If there is the DCI format, it can be appreciated that theterminal may know that the flexible subframe is used for downlinktransmission. The terminal measures non-period channel informationthrough a corresponding subframe in step 732. The information ismeasured to be transmitted when non-period channel information for acorresponding flexible subframe is requested. Step 732 may be performedafter a next step according to an implementation operation of theterminal. The terminal receives non-period channel information requestthrough a first downlink subframe from an eNodeB after the flexiblesubframe in step 733. The request of the non-period channel informationis received through a UL grant, and the UL grant may be restricted byrequesting only non-period channel information without PUSCH data. TheUL grant contains a flag designating whether the non-period channelinformation request is for a general downlink subframe or the flexiblesubframe.

Subsequently, it is determined whether a flag for discriminating thesubframe is 1 at step 734. If the flag for discriminating the subframeis 1, the terminal transmits non-period channel information for theflexible subframe through an uplink subframe corresponding to thedownlink subframe in step 735. The non-period channel informationcontains all of the channel information sent by upper layer signaling.If the flag for discriminating the subframe is 0, the terminal transmitsnon-period channel information for a general downlink subframe throughan uplink subframe corresponding to the downlink subframe in step 736.The non-period channel information contains all of channel informationsent by upper layer signaling.

FIG. 9 is a block diagram illustrating an apparatus for operating asub-frame of an eNodeB in a communication system according to anexemplary embodiment of the present invention.

Referring to FIG. 9, an eNodeB includes a transmitter composed of aPDCCH block 905, a PDSCH block 916, a PHICH block 924, and a multiplexer915, a receiver composed of a PUSCH block 930, a PUCCH block 939, and ademultiplexer 949, a controller 901, a scheduler 903. In thetransmitter, the PDCCH block 905 includes a DCI formatting unit 907, achannel coding unit 909, a rate matching unit 911, and a modulation unit913. The PDSCH block 916 include a data buffer 917, a channel codingunit 919, a rate matching unit 921, and a modulation unit 923. The PHICHblock 924 includes an HARQ ACK/NACK generation unit 925, a PHICHformatting unit 927, and a modulation unit 929. In the receiver, thePUSCH 930 includes a demodulation unit 937, a de-rate matching unit 935,a channel decoding unit 933, and a data acquiring unit 931. The PUCCHblock 939 includes a demodulation unit 947, a channel decoding unit 943,and an ACK/NACK or CQI acquiring unit 941.

The controller 901 reports an amount to be transmitted to the terminaland an amount of a resource available in a system to the scheduler 903using channel information received from the terminal according to anexemplary embodiment of the present invention.

The PDCCH block 905 configures a DCI under the control of the scheduler903, error correction performance is added to a DCI in the channelcoding unit 909, is rate-matched suited to an amount of a resource to beactually mapped by a rate matching unit 911, is modulated by themodulation unit 913, and is multiplexed with other signals in themultiplexing unit 915.

The PDSCH block 916 extracts data to be transmitted from a data butter917 under the control of the scheduler 903, error correction performanceis added to the extracted data in a channel coding unit 919, israte-matched suited to an amount of a resource to be actually mapped bya rate matching unit 921, is modulated by the modulation unit 923, andis multiplexed with other signals in the multiplexing unit 915.

The PHICH block 924 generates an HARQ ACK/NACK with respect to a PUSCHreceived by an HARQ ACK/NACK generation unit 925 from a terminal. TheHARQ ACK/NACK is configured so as to be suited to a PHICH channelstructure through a PHICH formatting unit 927, is modulated by themodulation unit 929, and is multiplexed with other signals in themultiplexing unit 915.

Further, the multiplexed signals are generated as an OrthogonalFrequency Division Multiplexing (OFDM) signal and the OFDM signal istransmitted to a terminal.

The PUSCH block 930 separates a PUSCH signal from a signal received froma terminal by a demultiplexing unit 949, is demodulated by ademodulation unit 937, symbols prior to rate matching are reconfiguredby a de-rate matching unit 935, is decoded by the channel decoding unit933, and PUSCH data are acquired by the data acquiring unit 931. Thedata acquiring unit 931 notifies of the presence of an error withrespect to a decoding result to the scheduler 903 to adjust generationof HARQ ACK/NACK, and applies the presence of the error with respect toa deciding result to the timing controller 901 to adjust downlink HARQACK/NACK timing.

The PUCCH block 939 separates a PUCCH signal from a signal received froma terminal using a demultiplexing unit 949 according to an exemplaryembodiment of the present invention, the separated PUCCH signal isdemodulated by the demodulation unit 947, the demodulated PUCCH signalis decoded by the channel decoding unit 943, and an uplink ACK/NACK orCQI is acquired by the ACK/NACK or CQI acquiring unit 941. The acquireduplink CQI is applied to a scheduler 903 and is used to determine atransmission Modulation and Coding Scheme (MCS) of the PDSCH.

In this case, in an apparatus for operating a subframe of a macroeNodeB, a controller determines and reports an uplink protectionsubframe for suppressing uplink transmission to neighboring eNodeBs.Further, the controller transmits scheduling information for a PUSCHthrough a downlink subframe corresponding to an uplink protectionsubframe. Here, the controller does not perform scheduling with respectto an uplink protection subframe such that uplink transmission from aterminal of a macro eNodeB is not performed through an uplink protectionsubframe. For example, when a subframe is operated according to a TDDUL-DL configuration #3, a macro eNodeB does not transmit schedulinginformation for a PUCCH through a subframe #9 but transmits schedulinginformation for a PUSCH. In the apparatus for operating a subframe of asmall eNodeB, the controller sets an uplink protection subframe reportedfrom a neighboring eNodeB as a flexible subframe. Moreover, thecontroller uses the flexible subframe for downlink transmission. In thiscase, the controller analyzes channel information of a flexible subframereceived from a terminal of a small eNodeB and uses it to schedule anext flexible subframe.

FIG. 10 is a block diagram illustrating an apparatus for transmittingchannel information of a terminal in a communication system according toan exemplary embodiment of the present invention.

Referring to FIG. 10, a terminal includes a transmitter composed of aPUCCH block 1005, a PUSCH block 1016, a multiplexing unit 1015; areceiver composed of a PHICH block 1024, a PDSCH block 1030, a PDCCHblock 1039, and a demultiplexer 1049; and a controller 1001. In thetransmitter, the PUCCH block 1005 includes a UCI formatting unit 1007, achannel coding unit 1009, a modulation unit 1013. The PUSCH block 1016includes a data buffer 1018, a channel coding unit 1019, a rate matchingunit 1021, and a modulator 1023. In the receiver, the PHICH block 1024include an HARQ ACK/NACK acquiring unit 1025, and a modulation unit1029. The PDSCH block 1030 include a demodulation unit 1037, a de-ratematching unit 1035, a channel decoding unit 1033, and a data acquiringunit 1031. PDCCH block 1039 includes a demodulation unit 1047, a de-ratematching unit 1045, a channel decoding unit 1043, and a DCI acquiringunit 1041.

The controller 1001 determines whether a flexible subframe from a DCIreceived from an eNodeB is used for downlink transmission, and reportsthe determination result to the PUCCH block 1005, the PUSCH block 1016,the PHICH 1024, the PDSCH 1030, and the PDCCH block 1039 such that theymay measure non-period channel information. A method of measuring andtransmitting the non-period channel information depends on the foregoingmethod of the invention.

The PUCCH block 1005 configures a HARQ ACK/NACK or CQI according to anexemplary embodiment of the present invention using Uplink ControlInformation (UCI) under the control of the controller 1001 by the UCIformatting unit 1007, error correction performance is added to the UCIby the channel coding unit 1009, is modulated by the modulation unit1013, and is multiplexed with other signals by the multiplexing unit1015.

The PUSCH block 1016 extracts data to be transmitted from the databuffer 1018, error correction performance is added to the extracted databy the channel coding unit 1019, is rate-matched suited to an amount ofa resource to be actually mapped by a rate matching unit 1021, ismodulated by the modulation unit 1023, and is multiplexed with othersignals in the multiplexing unit 1015.

Moreover, the multiplexed signals are generated as a Single CarrierFrequency Division Multiple Access (SC-FDMA) signal, and the SC-FDMAsignal is transmitted to an eNodeB.

The PHICH block 1024 separates a PHICH signal from a signal receivedfrom a terminal through a demultiplexing unit 1049, the separated PHICHsignal is demodulated by the demodulation unit 1029, and the presence ofan HARQ ACK/NACK with respect to the PUSCH is acquired by the HARQACK/NACK acquiring unit 1025. The PUSCH block 1030 separates a PUSCHsignal from a signal through a flexible subframe received from an eNodeBby a demultiplexing unit 1049, the separated PUSCH signal is demodulatedby a demodulation unit 1037, symbols prior to rate matching arereconfigured by a de-rate matching unit 1035, is decoded by the channeldecoding unit 1033, and PUSCH data are acquired by the data acquiringunit 1031. The data acquiring unit 1031 reports the presence of an errorwith respect to a decoding result to the PUCCH block 1005 to adjustgeneration of an uplink HARQ ACK/NACK.

The PDCCH block 1039 separates a PDCCH signal from a signal receivedfrom the eNodeB through the de-multiplexing unit 1049, the separatedPDCCH signal is demodulated by the demodulation unit 1047, symbols priorto rate matching are reconfigured by a de-rate matching unit 1045, thedemodulated PDCCH signal is decoded by the channel decoding unit 1043,and a DCI is acquired by the DCI acquiring unit 1041.

In this case, in the terminal of the small eNodeB, the controllermeasures non-period channel information from a flexible subframe usedfor downlink transmission. Moreover, the controller carries thenon-period channel information into at least one uplink subframe. Here,the controller may transmit the non-period channel information through aPUCCH in a preset uplink frame, namely, at least one uplink subframefrom a subframe #n+4. However, another flexible subframe after acorresponding flexible subframe is used for uplink transmission, thecontroller may stop transmission of non-period channel information andagain measure the non-period channel information. If the non-periodchannel information is requested from the small eNodeB through adownlink subframe after the flexible subframe, the controller maytransmit non-period channel information through a PUSCH in an uplinksubframe corresponding to a downlink subframe. In the meantime, if thenon-period channel information is requested from the small eNodeBthrough the flexible subframe, the controller may measure the non-periodchannel information. Moreover, the controller may transmit thenon-period channel information through a PUSCH in the preset subframe,for example, the subframe #n+4.

Exemplary embodiments of the present invention provide an approach whichdoes not influence resource use of a macro eNodeB while controllinginterference a small eNodeB terminal receives from the macro eNodeB. Inaddition, the exemplary embodiments of the present invention provide anapproach of transmitting downlink channel information which the smalleNodeB can refer to for scheduling when the small eNodeB uses theflexible subframe for downlink transmission in the TDD system.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined in the appended claims and their equivalents.

What is claimed is:
 1. A method of transmitting information by aterminal in a communication system, the method comprising: receiving,from a base station, a higher layer signal comprising informationrelated to at least two subframe sets; receiving, from the base station,control information comprising a request for channel status information(CSI) indicating a subframe set from the at least two subframe sets,wherein the control information indicates which one of the at least twosubframe sets is selected for generating CSI; generating CSI related toa first subframe of the indicated subframe set based on the controlinformation and the higher layer signal; and transmitting, to the basestation, the generated CSI on a second subframe.
 2. The method of claim1, wherein the request for the CSI comprises information indicating asubset of a subframe in a radio frame.
 3. The method of claim 1, whereinan interval between the first subframe and the second subframe is asmallest value greater than or equal to
 4. 4. The method of claim 1,wherein the first subframe is identified such that the first subframecorresponds to a valid downlink subframe or a valid special subframe andcontrol information on the first subframe comprises a requestcorresponding to the request for the CSI.
 5. A method of receivinginformation by a base station, the method comprising: transmitting, to aterminal, a higher layer signal comprising information related to atleast two subframe sets; transmitting, to the terminal, controlinformation comprising a request for channel status information (CSI)indicating a subframe set from the at least two subframe sets, whereinthe control information indicates which one of the at least two subframesets is selected for generating CSI, and wherein CSI related to a firstsubframe of the indicated subframe set is generated based on the controlinformation and the higher layer signal; and receiving, from theterminal, the CSI related to the first subframe on a second subframe. 6.The method of claim 5, wherein the request for the CSI comprisesinformation indicating a subset of a subframe in a radio frame.
 7. Themethod of claim 5, wherein an interval between the first subframe andthe second subframe is a smallest value greater than or equal to
 4. 8.The method of claim 5, wherein the first subframe is identified suchthat the first subframe corresponds to a valid downlink subframe or avalid special subframe and control information on the first subframecomprises a request corresponding to the request for the CSI.
 9. Aterminal for transmitting information, the terminal comprising: atransceiver for transmitting and receiving at least one signal; and aprocessor configured to: control the transceiver to receive, from a basestation, a higher layer signal comprising information related to atleast two subframe sets, control the transceiver to receive, from a basestation, control information comprising a request for channel statusinformation (CSI) indicating a subframe set from the at least twosubframe sets, wherein the control information indicates which one ofthe at least two subframe sets is selected for generating CSI, generateCSI related to a first subframe of the indicated subframe set based onthe control information and the higher layer signal, and control thetransceiver to transmit, to the base station, the generated CSI on asecond subframe.
 10. The terminal of claim 9, wherein the request forthe CSI comprises information indicating a subset of a subframe in aradio frame.
 11. The terminal of claim 9, wherein an interval betweenthe first subframe and the second subframe is a smallest value greaterthan or equal to
 4. 12. The terminal of claim 9, wherein the firstsubframe is identified such that the first subframe corresponds to avalid downlink subframe or a valid special subframe and controlinformation on the first subframe comprises a request corresponding tothe request for the CSI.
 13. A base station for receiving information,the base station comprising: a transceiver for transmitting andreceiving at least one signal; and a processor configured to: controlthe transceiver to transmit, to a terminal, a higher layer signalcomprising information related to at least two subframe sets, controlthe transceiver to transmit, to the terminal, control informationcomprising a request for channel status information (CSI) indicating asubframe set from the at least two subframe sets, wherein the controlinformation indicates which one of the at least two subframe sets isselected for generating CSI, and wherein CSI related to a first subframeof the indicated subframe set is generated based on the controlinformation and the higher layer signal, and control the transceiver toreceive, from the terminal, the CSI related to the first subframe on asecond subframe.
 14. The base station of claim 13, wherein the requestfor the CSI comprises information indicating a subset of a subframe in aradio frame.
 15. The base station of claim 13, wherein an intervalbetween the first subframe and the second subframe is a smallest valuegreater than or equal to
 4. 16. The base station of claim 13, whereinthe first subframe is identified such that the first subframecorresponds to a valid downlink subframe or a valid special subframe andcontrol information on the first subframe comprises a requestcorresponding to the request for the CSI.